The present invention relates in general to dishwashers, and more particularly to pumps, sieves, and filters in dishwashers.
Prior Art
By means of the circulation pump in a dishwasher, water is distributed to nozzles which are provided in the tub and which are placed on one or several rotating arms so that water is sprayed on the dishes. By means of a drain pump, the water is emptied from the dishwasher when the dishwashing cycle has been completed.
Dishwashers of the kind described above are known in the prior art, and are usually equipped with devices preventing large particles, such as food scraps and the like, from entering the circulation path, since such particles can clog the nozzles. In the most simple version, these devices comprises a coarse sieve which is situated above the dishwater collecting container and through which water flows down into the container. The sieve can be removed and cleaned under flowing water. The use of a coarse sieve means that it is possible to remove a major part of the large particles in the tub during the emptying period with the aid of the drain pump, and also with a minimal risk of clogging the sieve, but it also means that comparatively large particles can follow the water into the circulation path and clog the nozzles, requiring that the nozzles be cleaned regularly.
It is also known from the prior art to use fine sieves and filters of different types, such as micro-filters, i.e., very fine filters, in order to remove almost all particles in the circulating water. Because such filters have a large flow resistance and because they also have a great tendency to become clogged, large filter areas and short intervals between cleaning are demanded. Frequent cleaning is both troublesome and time-consuming for the operator. A large, upwardly facing filter area also leaves the filter open to damage by knives, forks, spoons, or the like falling from above.
In order to achieve cleaner circulatiing water with a limited filter area, it has benn suggested to use a fine sieve and replace a part of the fine sieve with a small filter area, the openings of the fine sieve being less than the openings of the nozzles but considerably larger than the openings of the filter. It is thereby expected that the circulating water, at least sometime during the dishwashing cycle, passes throough the filter and is then cleaned of the fine particles. However, these filters are difficult to clean, and they are easily clogged.